At night, street lights help illuminate the roads around us. They consist of lamp heads, poles, bases, cables, and other necessary components. Although you are familiar with them, it will be helpful to learn more about standards about street lighting, especially when you are planning to buy one or several of these lights. You can’t miss the following article which introduces the basic parameters and lighting standards for street lights. Let’s dive in!
History of street lights
Street lights were first used in 1417 in London. As time passed, the street lights changed from coal-gas lamps to electrical arc lamps, and then turned into incandescent lamps in 1879. With the same power, incandescent lamps can generate more light. And the 20th century has witnessed the invention of low-pressure sodium and high-pressure sodium lamps. Later, as research found that white light is more helpful for drivers to see the road condition more clearly, people also applied metal halide lighting systems. Now, as the new technology of LED street lights has shown its significant advantages, most countries are replacing their street lights with LED or solar ones. Moreover, experts are also developing the smart street lights.
Parameters about street lighting
The light source emits a certain amount of energy, which is then received by the human eye. Luminous flux (Φ) measures this amount of light. Luminous flux indicates the amount of radiated light energy per unit time, and the unit is lumens/lm. Another unit is for luminous intensity, which is called candela (cd).
Illuminance (E) indicates the amount of illumination on the surface area, which is the luminous flux of visible light received per unit area, and the unit is lx. lm/m2 means that 1 lm of light illuminates an area of 1 square meter.
Utilization coefficient (U) measures the light that arrives directly on the road, so it is the ratio of the luminous flux on the surface to the total amount of it. The height of the street lights, the width of the road, the elevation angle, and other factors can affect its value.
Average road surface luminance
The average road surface luminance (Eav) is the average value of the illuminance at the points on the road surface set by the regulations of the International Commission on Illumination (CIE).
Overall uniformity of road surface luminance
Overall uniformity of road surface luminance is the ratio of the minimum to the average value of the brightness of the road.
Because of glare, drivers may feel uncomfortable and find it hard to observe objects. An inappropriate brightness distribution, brightness range, or inappropriate contrast may cause glare. Extreme glare may lead to light pollution, but it will become a myth when the design of the light is reasonable enough.
Threshold incremen (Ti)
If the glare causes disability, it is essential to limit the glare to a safe level. And the method is to make the contrast between an object and the background more obvious. The percentage of this increase is measured as threshold incremen.
Surround ratio (SR)
The ratio of average illuminance on a 5-meter-wide road surface to that on a 5-meter-wide area besides the road
Different road types and the requirements
For different types of road, they need to apply different standards of lighting to ensure the lighting effect is qualified and the cost is ideal. To determine the lighting used, the International Commission on Illumination divided the roads into five grades, from M1 to M5, as shown in the table below:
|Highway, motorway, or expressway with divided lanes that doesn’t have level crossings or fully controlled entry and exit||M1/M2/M3|
|Expressways and double lanes||M1/M2|
|Important urban traffic roads, radial roads, and inter-regional distribution roads||M2/M3|
|Less important roads like distribution roads in the suburbs and major residential areas||M4/M5|
For these five grades, the requirements are as shown in the table below:
|All roads||Roads with few or no intersections||Roads with sidewalk|
Types of street lights
Classified by height
Conventional road lighting
Lights are installed on the poles at a height of under fifteen meters. These street lights are set on one or two sides of the road at a certain interval. Since the light is vertical to the road, it can distribute most of the light on the road.
High mast lighting
The poles of high-mast lighting are usually twenty meters or more. And the higher the poles are, the more areas they can illuminate.
The height of this type of street light is between 15 and 20 meters, and it can work both as conventional lighting and high mast lighting.
Classified by light distribution characteristics
There are three types of street lights: cut-off luminaires, semi-cut-off luminaires, and non-cut-off luminaires. The most obvious differences between them are their abilities to prevent glare and the places people use them.
The angle of the lighting of the cut-off luminaire has the most strict limitation. Because of this limitation, the contrast between the surrounding environment and the road can be obvious enough to reduce the glare effect. Besides, it is also a way to increase the brightness and uniformity of the light, providing a more suitable lighting effect.
Maximum light intensity values at the maximum luminous angle
|Type||Direction of the light with maximum intensity||Intensity at certain angle|
*No matter how much luminous flux the bulb emits, the maximum light intensity must not exceed 1000 cd.
Cut-off luminaire: Expressways, main roads leading to large public buildings, roads in city centers or commercial centers, and large traffic hubs
Semi-cut-off luminaire: Secondary trunk and branch roads.
Non-cut-off luminaire: As diffuse and decorative lights, they are suitable for garden lighting or sidewalk lighting.
The standards of LED lights may vary, but there are some common standards for street lighting to achieve the best lighting effect. Considering the road types, there are many things to consider, such as the required lamp types, how to prevent glare, the value of the maximum light intensity, and so on. If you are not clear about any one of the above questions, you can come to Mokolight where you can get professional consultation. Mokolight has put efforts into the development of LED lighting for more than 16 years and produced top-notch LED lights. We are clear about the standards of street lighting and which product suit your project best. And our products are all certified and strictly tested. You will be sure to find LED street lights of the highest quality that will light up the roads in the most appropriate way.